It’s an unnerving — no, genuinely scary — experience to see Concord Floral. For one thing it’s about teenagers and what it’s like to be one. And that can unsettle your adult equilibrium since we all have one of our very own, the one we once were, inside us.

Doesn’t it feel like the time in life where the storied “innocence of childhood” has vanished into thin air, but your grown-up self is still forming, mysteriously and in secret? “All parents are a little stupid,” says one of the play’s 10 characters in a chilly little insight. “They make themselves that way or they’ll go insane worrying about all the things they secretly know to be true.”

Concord Floral, by the young Canadian star playwright Jordan Tannahill, is a ghost story of sorts, a haunting and an exorcism. Its inspiration is Boccaccio’s 14th century Decameron, in which young people flee plague-struck Florence for a countryside villa, and tell stories, one a night, to pass the time. This is suburban Ontario, and Concord Floral is a long-abandoned greenhouse in a field where teenagers go to be free, stay up late, drink, smoke weed, have sex.

On a dark night Nearly (Leila Raye-Crofton) and her friend Rosa (Helen Belay) are in the greenhouse, with only a cellphone flashlight app for light. The phone, still lit, gets dropped into a well. And the girls can’t unsee what they see: it’s glowing from inside a dead body.

A dark shadow is over the town: the plague? the Angel of Death as one character speculates? The characters, who all have individual lives and hopes, dreams, and nightmares, share something damning; they’re haunted together, by an act of wanton cruelty, by shared guilt.

I shouldn’t tell you more, except to say that the play is a beautiful piece of construction, with metaphorical resonances, a text that threads the poetic through the sound of real teens talking, the dramatic and the presentational (with more than a whiff of I Know What You Did Last Summer). The characters include a ghost, an abandoned couch, a bobolink, a fox, and the greenhouse itself (Marguerite Lawler) who reflects on the possibility of mercy in a world full of cruelty towards outsiders.

Mieko Ouchi directs an ensemble cast of young U of A theatre school grads, who perform with raw honesty and invention in a production lit by cellphone. A stunning piece of theatre.